During physical exercise, the body is subjected to stresses and strains beyond those normally encountered in everyday activities. These stresses and strains increase the risk of injury to areas of the body such as the joints, and care should be taken to minimise such risks wherever possible during training. In the performance of exercises for training the abdominal muscles, the joint between the pelvis and the spine is particularly at risk. To minimise the risk of injury to this joint, it is beneficial to maintain the pelvis in a position substantially at the mid-point of its range of anterior to posterior rotation about the joint. This position is referred to herein as neutral pelvic alignment.
The ideal body position for maintaining neutral pelvic alignment is referred to herein as the half-kneeling position. This involves the user being supported by his or her knees and buttocks only, with a somewhat larger angle being formed between the abdomen and the upper legs than is customary in a normal seated position.
Conventional fitness apparatus for training a user's abdominal muscles tends not to operate with the user in positions which promote neutral pelvic alignment. Additionally, many known abdominal training devices rely solely on weight-stacks or elastic resistance elements to provide the resistive force which the user must overcome during exercise. The use of weight-stacks makes the product difficult and expensive to ship, and cumbersome to move once installed, whilst the use of elastic resistance elements alone results in the resistive load increasing exponentially as the material is stretched. Unless used in combination with other resistive loads, this provides an unnatural load and decreases the specificity of the exercise, i.e. the targeting of a particular exercise to a particular group of muscles.
Exercise apparatus enabling a user to perform abdominal muscle training exercise from a half-kneeling position so as to promote neutral pelvic alignment is described in the applicant's co-pending International Patent Application No. PCT/GB2006/050263. The exercise apparatus described therein comprises a lever frame linked to a support frame at a pivot. The lever frame has first and second arms joined at a central junction also forming a fulcrum. The support frame has a base member with a seat portion. The apparatus is operated by the user pushing the first arm away from his or her body causing the lever frame to rotate about its fulcrum. This lifts the second arm, which in turn causes the seat portion to lift and/or tilt.
The user's abdominal muscles are thus exercised in lifting his or her body mass, thus ensuring a more natural load than when working only against applied loads from weight stacks and resistance elements. The apparatus described in PCT/GB2006/050263 is also capable of being adapted for use as a static kneel chair, in which the user may easily and safely mount and dismount from the rear of the seat.